The present invention relates to a printed wiring board which permits easy mounting of electrical parts and the like and which not only enables spaces to be saved, but also facilitates manufacturing.
Electrical components tend to increase in number from the requirements for an improvement in the functions of products of, for example, automobiles. For this reason, in order to use limited spaces efficiently, it is required that electrical parts and the like be easily mounted and that spaces necessary for their mounting be reduced.
Therefore, in performing the wiring and branching of electric wires for automobiles and the like, there has been used an electric connection box which is constructed so that parts, such as connections to wire harness, fuses and relays, are collected in one place and connected there. And as the above-described electric connection box, there has been known an electric connection box in which a rigid printed wiring board that is constructed in such a manner that a circuit is formed on the surface of a hard base material is used as a wiring material for distributing power from a power source (hereinafter referred to as an internal circuit).
A method of manufacturing a rigid printed wiring board 100 by prior art will be described with reference to FIGS. 15(a) to 15(c).
According to the prior art, a laminate 103 which is obtained by laminating a conductor layer 102, such as copper foil and silver foil, each on a front surface and a rear surface of a hard base material 101 made of an insulating material, is used (refer to FIG. 15(a)), and through holes 104 (a via through hole 104a which ensures electrically conducting properties for the conductor layers 102 on the front and rear surfaces and a mounting through hole 104b for providing a connection terminal 20) are formed by planting a substrate through-hole provided by drilling the laminate 103. At the same time, by etching the above-described laminate 103, a circuit 102a is formed on the front and rear surfaces of the hard base material 101 (refer to FIG. 15(b)), and the front surface of the circuit is coated with a resist (an insulating material) 105, whereby a rigid printed wiring board 100 is manufactured (refer to FIG. 15(c)). Also, a multilayer wiring board has been similarly manufactured by performing laminating and pressing.
In a case where by use of the prior art, an electrical part is mounted on the rigid printed wiring board 100 and a wiring material (a substrate circuit) of an internal circuit as used in electrical equipment is formed, as shown in FIGS. 16(a) to 16(c), the mounting through hole 104b for the insertion of the connection terminal 20 is provided beforehand in a connector for the connection to the electrical part and a connection to the electrical part, such as a fuse and a relay. After the press fitting of the connection terminal 20 into the above-described mounting through hole 104b, the rigid printed wiring board 100 and the connection terminal 20 are connected together after going through the step of flow soldering or reflow soldering.
As shown in FIG. 16(a), in connecting the connection terminal 20 to the rigid printed wiring board 100 which is provided with the via through hole 104a for ensuring the conducting properties of the circuits formed on the front and rear surfaces of the substrate and the mounting through hole 104b into which the connection terminal 20 is press fitted, because the above-described mounting through hole 104b is formed from a hole which pierces through the substrate, in a case where a substrate circuit in which the connection terminals 20 are provided at prescribed positions each on the front surface and rear surface of the substrate, it is necessary to design a substrate circuit in such a manner that the positions of the connection terminals 20 do not overlap on the front and rear surfaces. Therefore, the prior part had the disadvantage that the projected area of the substrate circuit becomes large.
In forming a substrate circuit in which the connection terminals 20 are provided at prescribed positions each on the front surface and rear surface of the substrate, it was necessary to solder the connection terminals 20 by performing the step of fixing the connection terminals 20 provided at prescribed positions on the front surface of the rigid printed wiring board 100 by solders 21 as shown in FIG. 16(b), and the step of fixing the connection terminals 20 provided at prescribed positions on the rear surface of the rigid printed wiring board 100 by solders 21 as shown in FIG. 16(c). That is, it has been necessary to perform the soldering step twice.
Therefore, as shown in FIGS. 17(a) and 17(b), there have been proposed techniques which involve connecting two rigid printed wiring boards 100, in each of which a connection terminal 20 is provided at a prescribed position on a front surface, by means of an electric wire 107, and bending the two rigid printed wiring boards 100 in an electric wire portion, whereby a substrate circuit in which the connection terminals 20 are provided at prescribed positions on both surfaces is obtained (refer to Patent Document 1, for example).    [Patent Document 1] Japanese Patent Application No. 2004-192546